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The microstrip antenna have been widely used because of their good characteistics, such as electrically thin, light weight, low cost, conformable and so on. However, the electrical performance of the basic microstrip antenna suffers from a number of serious drawbacks, including very narrow band width, high feed network and low gain. As the rapidly developing of markets, suggest that the demand for microstrip antennas will increase even further. In the meantime,it calls for the development of multibandFirstly, the Koch fractal antenna is proposed in this thesis, and it can reduce the size of microstrip patch antenna. And then, another fractal antenna called sieprinski is proposed. It can not only reduce the antenna’s size, but also meet the need of multiband, and its modified sieprinski can enhance the poor matching. At the same time, we proposed another fractal antenna called Crown Square Fractal Antenna, which can achieve the goal of multiband. What’s more, it can be coordinate easily. In practice, we used the Fractal antenna to cover the frequency of global positioning system (GPS, 1.57542GHz), digital multimedia broadcasting (DMB, 2.6-2.655GHz). The simulated and tested result mach well.Secondly, we introduce a new differentially-driven microstrip antenna, with the use of H-shape slot. We make use of the higher order mode radiation in addition to the intrinsic domain mode, yielding a very wide impedance bandwidth, which can reach to about 32%. Most importantly, with the use of a U-shaped ground, we can make the gain more stable, which is very important in modern devices. In order to improve the poor match work, we can use the fractal to H-shape slot microstrip patch antenna. It is proved very useful.At last, we introduce a new gain enhancement method for microstrip antenna through multiple superstrates. There are very little papers we can refer to. So we proposed four factors which can impact the gain of the antenna. On the other hand, duo to several attractive advantages of microstrip patch antenna array, we made 2 elements and 4 elements ( 2×2), and find that the gain increases by the rapid of 2.5dB because of dielectric loss.
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